1. Field of the Invention
The present invention relates generally to a gas turbine engine, and more specifically to a cooling circuit for an industrial gas turbine blade outer air seal inter-segment gap.
2. Description of the Related Art Including Information Disclosed Under 37 CFR 1.97 and 1.98
A gas turbine engine includes a turbine with multiple rows or stages of rotor blades with stator vanes located upstream to guide a hot gas flow through the rotor blades. The rows of rotor blades rotate within an outer shroud that forms a blade outer air seal (BOAS) with a small gap or blade tip clearance to minimize leakage across the blade tips. In an industrial gas turbine engine, the outer shroud is formed from an annular arrangement of shroud segments each with relatively large gaps between adjacent segments to allow for metal expansion during operation and transients of the engine. These shroud segments are loose fitting at cold temperature and thermally expand at steady state temperature to close the gaps.
In order to limit leakage across the segment gaps, axial slots are formed in the segment mate faces in which a seal is placed. FIG. 1 shows a prior art blade outer air seal design with two adjacent shroud segments having axial slots facing each other and with a flat seal secured within the adjacent slots. Cooling air holes are formed along the lower surface of the shroud segments to pass cooling air and provide some cooling to the segments. FIG. 2 shows a close-up view of the mate face of two shroud segments with the axial gap and the seal within the slots. The FIGS. 1 and 2 BOAS design lacks adequate cooling and sealing to prevent hot gas ingestion along the axial slot. Hot gas flows in and out along the inter-segment gaps and creates an over-temperature at the BOAS edges corresponding to the hot gas injection location.